Cetrorelix

How it works

It competitively blocks pituitary GnRH receptors, producing an immediate, dose-dependent suppression of luteinising hormone and thereby preventing a premature LH surge.

Prescribing in practice

• It must be used as part of a specialist-supervised assisted conception protocol to prevent premature ovulation, with timing relative to gonadotrophin stimulation defined by the protocol.
• Unlike GnRH agonists it produces immediate suppression without an initial flare, so it is started during ongoing follicular stimulation.
• Local injection-site reactions are common and ovarian hyperstimulation syndrome remains a risk of the overall stimulation cycle.

Monitoring

Ovarian response is monitored by ultrasound follicle tracking and hormone levels as part of the stimulation cycle.

Counselling the patient

• This injection prevents your eggs being released too early during fertility treatment.
• Injection-site redness or itching is common and usually mild.
• Report severe abdominal pain, bloating, or breathlessness, which may indicate ovarian hyperstimulation.

Evidence & guidelines

GnRH antagonist protocols are an established approach in assisted reproduction and are associated with a lower risk of ovarian hyperstimulation syndrome than long agonist protocols.